Assembly of disease-relevant pathways in the mouse The mouse continues to provide important information concerning the role of genes in both normative biology and pathogenesis of disease. Mouse models have been identified and developed for many diseases, including Alzheimer's, autoimmune diseases, cardiovascular diseases and cancer. These include complex models unique to specific inbred mouse lines such as the diabetic NOD mouse line and models that have been generated by manipulation of the mouse germline. These manipulations include the introduction of transgenes, the removal of genes and the introduction of point mutations into mouse genes by targeted mutagenesis. Often, the development of models requires the breeding of mice to generate animals carrying multiple mutations. While mouse models have been enormously useful in understanding the pathogenesis of disease, in many cases they are not amenable to the evaluation of new therapeutics. For example, few of the therapeutic antibodies in development cross react with the orthologous mouse gene, and the distribution of Fc receptors between species and differences in antibody clearance makes evaluation of these drugs difficult. Similarly, differences between human and mouse in the metabolism of small molecules limit the usefulness of many mouse disease models for the study of the efficacy of this class of therapeutics. Furthermore, in the majority of cases, the genetic architecture of most mouse disease models developed to date does not resemble that of individuals at risk for disease. Perhaps more importantly, the models are not amenable to further rapid genetic manipulation as new genetic factors influencing disease pathogenesis are identified. In addition, when novel disease associated polymorphisms are discovered, few of the models allow easy testing of the functional implications of these variants. In this application we propose the development of strategies and methods for the rapid generation of mouse models useful for: 1) the functional evaluation of disease associated polymorphisms, 2) the study of gene-gene interactions in disease pathogenesis, and 3) testing of therapeutics directed against these disease associated genes. Specifically we propose to develop cell and mouse lines useful for such evaluation of the -secretase complex. This multi-subunit protease complex mediates intramembranous cleavage of a number of important molecules including amyloid precursor protein (APP). Cleavage of APP by -secretase yields -amyloid, a primary component of plaques characteristic of Alzheimer's disease.